1. Field of the Invention
The present invention relates to a handpiece with a removable handpiece sleeve for worktools or dental implements which are releasably insertable therein with the assistance of a collet which is rotatable through the intermediary of a drive shaft, wherein the collet is conically configured on its exterior at the end thereof facing towards the dental implement and cooperates with the end correspondingly conically configured of a spindle sleeve facing towards the implement, and in which the contact between the two conically-configured ends facing towards the implement is produced by means of a spring which is inserted intermediate an annular shoulder on the spindle sleeve and a clamping sleeve, and wherein the collet is releasable through a twisting turning imparted to the handpiece sleeve.
2. Discussion of the Prior Art
A handpiece of that type is essentially known from the disclosure of German Laid-Open Patent Appln. 22 34 231. In that particular instance, the inventive concept contemplates that for affording an easy handling or action during the actuation of a threaded sleeve for the formation of and elimination of a spring tension for effectuating the clamping of the implement, screwthread-like grooves are formed in the threaded sleeve and in the inner wall of an internal sleeve of the handpiece, and whereby suitable roll bodies are inserted into the grooves.
This prior art construction is encumbered by a plurality of disadvantages. On the one hand, the two screwthread-like grooves and the insertion of roll bodies entails a significant increase in the costs of manufacture and in the assembling of parts. Furthermore, the clamping force or; in essence, adjusting force can only be applied from one side, with the consequence of resulting in a poor centering of the dental implement. Because of the principle of utilizing a screwthread, notwithstanding the employment of roll bodies, the actuation is difficult in its handling, especially in such instances when it is impossible to prevent the ingress or penetrating of dirt. Moreover, there can also be encountered an automatic or spontaneous locking action, as a result of which the implement is retained in position at only a low or inadequate amount of force.